McIlroy was two over par for the day after bogeys on the 10th and 11th but
rallied superbly to birdie the 13th, 15th and 16th, only to drop shots on the
last two holes.
The last 13 Masters champions were all inside the top 10 after the opening round and McIlroy found himself outside the top 40 at the time of signing his card.
“I felt the course was there,” McIlroy said. “It’s soft. There’s not much wind. I made five birdies, that wasn’t the problem. I just made too many mistakes. And I’m making mistakes from pretty simple positions, just off the side of the green, 17 and 18 being prime examples of that.
“I’m going to go to the putting green right now and try to figure this out, just sort of reads more than anything else. I over-read a few early on, and then I started to under-read them coming in.
“I think just whenever the greens are a little slower, they don’t break as much. The greens are maybe two or three feet slower than they usually are, just because it’s been so soft and the rain. They will get faster as the week goes on, so it’s just a matter of adjusting.”
McIlroy’s 73 was his worst opening round since a 74 in 2010 and the Northern Irishman added: “You know you’re going to have chances. There’s birdie opportunities.
“I can accept mistakes if I’m trying and it’s not a mental error, but six bogeys out there is a little too many and I’m just going to need to tidy that up over the next few days.”